<template>
  <view class="u-wrap">
    <view class="u-menu-wrap">
      <!-- 左侧分类滚动 -->
      <scroll-view scroll-y scroll-with-animation class="u-tab-view menu-scroll-view"
                   :scroll-top="scrollTop"
                   :scroll-into-view="itemId">
        <view v-for="(item,index) in tabbar" :key="index" class="u-tab-item" :class="[current == index ? 'u-tab-item-active' : '']"
              @tap.stop="swichMenu(index)">
          <text class="u-line-1">{{item.name | formatText}}</text>
        </view>
      </scroll-view>
      <!-- S左侧分类滚动 -->

      <!-- S 右侧产品列表 -->
      <scroll-view :scroll-top="scrollRightTop" scroll-y scroll-with-animation class="right-box" @scroll="rightScroll">
        <view class="page-view">
          <view class="class-item" :id="'item' + index" v-for="(item , index) in tabbar" :key="index">
            <view class="item-title">
              <text>{{item.name}}</text>
            </view>
            <view class="item-container">
              <view class="thumb-box" v-for="(item1, index1) in item.foods" :key="index1" @click="handlerClick(item1.id, item1.name)">
                <uniImage v-if="item1.icon != ''" class="item-menu-image" :src="item1.pic" ></uniImage>
                <view v-else class="item-menu-image row-c" style="background-color: #F4F6F8;">
                  <text style="font-size: 20rpx;color: #d0d0d0;">加载失败</text>
                </view>
                <view class="item-menu-name">{{item1.name | formatText }}</view>
              </view>
            </view>
          </view>
        </view>
      </scroll-view>
      <!-- E 右侧产品列表 -->

    </view>
  </view>
</template>
<script>
import {getProductClass , getProductList} from "@/models/product";
export default {
  data() {
    return {
      scrollTop: 0, //tab标题的滚动条位置
      oldScrollTop: 0, // tab标题的滚动条旧位置
      current: 0, // 预设当前项的值
      menuHeight: 0, // 左边菜单的高度
      menuItemHeight: 0, // 左边菜单item的高度
      itemId: '', // 栏目右边scroll-view用于滚动的id
      tabbar: [], // 渲染的数据，放在最后供你们测试
      arr: [], // 储存距离顶部高度的数组
      scrollRightTop: 0, // 右边栏目scroll-view的滚动条高度
      timer: null // 定时器
    }
  },
  onShow() {
    this.productClassData()
    this.getMenuItemTop()
    // uni.getLocation({
    //   type: 'gcj02',
    //   geocode: true,
    //   success: function (res) {
    //     console.log(res.latitude)
    //     console.log(res.longitude)
    //   },
    // fail: (e) => {
    // console.log(e)
    // }
    // });
  },

  methods: {
    /**
     *  获取分类以及产品列表
     */
    async productClassData(){
      const resultClass = await getProductClass({"limit":0})
      const resultList = await getProductList({"limit":0});
      const toolbar = resultClass.data.data.map((res)=>{
        let productclass = resultList.data.data.filter(result=>result.pid === res.classid)
        return {
          "name":res.classname,
          "foods":productclass
        }
      })
      this.tabbar = toolbar
    },

    getElRect(elClass, dataVal) {
      new Promise((resolve, reject) => {
        const query = uni.createSelectorQuery().in(this);
        query.select('.' + elClass).fields({
          size: true
        }, res => {
          // 如果节点尚未生成，res值为null，循环调用执行
          if (!res) {
            setTimeout(() => {
              this.getElRect(elClass);
            }, 10);
            return;
          }
          this[dataVal] = res.height;
          resolve();
        }).exec();
      })
    },


    /**
     * 获取右边菜单每个item到顶部的距离
     * 储存到 arr 数组里面用于后面滚动判断
     */
    getMenuItemTop() {
      new Promise(resolve => {
        let selectorQuery = uni.createSelectorQuery();
        selectorQuery.selectAll('.class-item').boundingClientRect((rects) => {
          // 如果节点尚未生成，rects值为[](因为用selectAll，所以返回的是数组)，循环调用执行
          if(!rects.length) {
            setTimeout(() => {
              this.getMenuItemTop();
            }, 10);
            return ;
          }
          rects.forEach((rect) => {
            // 视情况而定，这里减去rects[0].top，是因为第一项顶部可能不是贴到导航栏(比如有个搜索框的情况)
            // this.arr.push(rect.top - rects[0].top);
            this.arr.push(rect.top)
            resolve();
          })
        }).exec()
      })
    },
    /**
     * 观测元素相交状态
     * 检测右边scroll-view的id为itemxx的元素与right-box的相交状态
     * 如果跟.right-box底部相交，就动态设置左边栏目的活动状态
     */
    async observer() {
      this.tabbar.map((val, index) => {
        let observer = uni.createIntersectionObserver(this);
        observer.relativeTo('.right-box', {
          top: 0
        }).observe('#item' + index, res => {
          if (res.intersectionRatio > 0) {
            let id = res.id.substring(4);
            this.leftMenuStatus(id);
          }
        })
      })
    },
    /**
     * 设置左边菜单的滚动状态
     * @index 传入的 ID
     */
    async leftMenuStatus(index) {
      this.current = index;
      // 如果为0，意味着尚未初始化
      if (this.menuHeight == 0 || this.menuItemHeight == 0) {
        await this.getElRect('menu-scroll-view', 'menuHeight');
        await this.getElRect('u-tab-item', 'menuItemHeight');
      }
      // 将菜单活动item垂直居中
      this.scrollTop = index * this.menuItemHeight + this.menuItemHeight / 2 - this.menuHeight / 2;
    },

    /**
     * 点击左边的栏目切换
     * @index 传入的 ID
     */
    async swichMenu(index) {
      if(this.arr.length == 0) {
        await this.getMenuItemTop();
      }
      if (index == this.current) return;
      this.scrollRightTop = this.oldScrollTop;
      this.$nextTick(function(){
        this.scrollRightTop = this.arr[index];
        this.current = index;
        this.leftMenuStatus(index);
      })
    },
    /**
     * 右边菜单滚动
     * 如果不存在height2，意味着数据循环已经到了最后一个，设置左边菜单为最后一项即可
     */
    async rightScroll(e) {
      this.oldScrollTop = e.detail.scrollTop;
      if(this.arr.length == 0) {
        await this.getMenuItemTop();
      }
      if(this.timer) return ;
      if(!this.menuHeight) {
        await this.getElRect('menu-scroll-view', 'menuHeight');
      }
      setTimeout(() => { // 节流
        this.timer = null;
        let scrollHeight = e.detail.scrollTop + 20;
        for (let i = 0; i < this.arr.length; i++) {
          let height1 = this.arr[i];
          let height2 = this.arr[i + 1];
          if (!height2 || scrollHeight >= height1 && scrollHeight < height2) {
            this.leftMenuStatus(i);
            return ;
          }
        }
      }, 10)
    },

    handlerClick(id,name){
      const url = `./product-detail?id=`+id
      uni.navigateTo({url:url});
    }

  },
  filters:{
    formatText(text){
      return text.substr(0,4)
    }
  }

}
</script>

<style>
.u-wrap {
  /* #ifdef H5 */
  height: calc(100vh - var(--window-top));
  /* #endif */
  display: flex;
  flex-direction: column;
  height: 100vh;
}

.u-search-box {
  padding: 18rpx 30rpx;
}

.u-menu-wrap {
  flex: 1;
  display: flex;
  overflow: hidden;
}

.u-tab-view {
  width: 200rpx;
  height: 100%;
}

.u-tab-item {
  height: 110rpx;
  background: #f6f6f6;
  box-sizing: border-box;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 26rpx;
  color: #444;
  font-weight: 400;
  line-height: 1;
}

.u-tab-item-active {
  position: relative;
  color: #06A446;
  font-size: 30rpx;
  font-weight: 500;
  background: #D6FFE7;
}

.u-tab-item-active::before {
  content: "";
  position: absolute;
  border-left: 4px solid #06A446;
  height: 52rpx;
  left: 0;
  top: 29rpx;
}

.u-tab-view {
  height: 100%;
}

.right-box {
  background-color: rgb(250, 250, 250);
}

.page-view {
  padding: 16rpx;
}

.class-item {
  margin-bottom: 30rpx;
  background-color: #fff;
  padding: 16rpx;
  border-radius: 8rpx;
}

.class-item:last-child {
  min-height: 100vh;
}

.item-title {
  font-size: 26rpx;
  color: $u-main-color;
  font-weight: bold;
}

.item-menu-name {
  margin-top: 8rpx;
  font-weight: normal;
  font-size: 24rpx;
  color: $u-main-color;
}

.item-container {
  display: flex;
  flex-wrap: wrap;
}

.thumb-box {
  width: 33.333333%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  margin-top: 20rpx;
}

.item-menu-image {
  width: 120rpx;
  height: 120rpx;
}
</style>
